The invention relates to the area of chemistry and petrochemistry, more precisely to a process for producing phenol and acetone by the cumene method.
The phenol that is used as the starting material, which is produced by the decomposition of cumyl hydroperoxide with an acidic catalyst, does not satisfy consumer requirements, since it contains admixtures of hydroxyacetone (HA), 2-methylbenzofuran (2-MBF), α-methylstyrene (AMS), acetophenone (AP), mesityl oxide (MO), and dimethylphenylcarbinol (DMPC), and needs to have the indicated impurities removed.
Relatively pure end product phenol is obtained by means of fractional distillation of the decomposition product of cumyl hydroperoxide with separation from the lower-boiling and higher-boiling components [U.S. Pat No. 4,251,325 (1978)]. However, even with careful operation of the rectifier, the phenol that is isolated contains such impurities as HA and 2-methylbenzofuran in quantities which are relatively small, but are still undesirable.
Processes are known for purifying the phenol that is used as the starting material which involve the use of various heterogeneous catalysts which convert the impurities listed above almost entirely into high-boiling compounds which can later be separated from the product phenol by distillation. One exception is HA, which can be converted into 2-methylbenzofuran or into higher-boiling products, depending on the efficiency of the catalyst. Thus, during the catalytic conversion the only impurity—2-methylbenzofuran—can accumulate in the catalysis product, complicating the subsequent separation process.
For example, a process is known for producing phenol of high purity from the phenol that is used as the starting material, which is produced by the decomposition of cumyl hydroperoxide with an acidic catalyst, by placing it in contact with a heterogeneous catalyst, which is a gamma aluminum oxide having a certain specific surface and a certain acidity of the surface centers. In the process, the aliphatic and aromatic carbonyl compounds, which are present in the starting phenol, are converted into high-boiling products, which are relatively easily removed from the end product by rectification [U.S. Pat. No. 5,264,636 (1992)]. The disadvantage of this process is the insufficiently high activity of the catalyst, especially when the content of impurities in the starting phenol is relatively small (0.1% by mass and less), which means that the 2-methylbenzofuran content of the end product is reduced to only a small extent.
A process is also known where phenol is purified by removing from it the side products of the cumene oxidizing process. This process involves treating the starting phenol by placing it in contact with a catalyst which is activated aluminosilicate, and then separating the resulting high-boiling components by distillation [U.S. Pat. No. 2,910,511 (1956)—prototype].